CRITICS QUESTION NASA ON SAFETY OF THE SHUTTLES

By JOHN SCHWARTZ

Published: February 7, 2005

As NASA prepares to return the space shuttle to orbit this spring, a debate over whether the fleet is as safe as it should be has been building inside and outside the space agency.

There is widespread agreement that the National Aeronautics and Space Administration, prodded by a searing report from the expert panel that investigated the loss of the Columbia two years ago, has made the fleet safer, and the agency is moving full speed toward launching as early as May. But critics, citing internal agency documents and NASA's own acknowledgment that it has not made all the improvements it committed to, contend that the agency is rushing back to the unforgiving environment of space with too much of the job left undone.

The Columbia broke up over Texas as it returned to earth on the morning of Feb. 1, 2003, killing the seven astronauts onboard. A hole punched in the leading edge of the left wing by an errant piece of insulating foam 82 seconds after liftoff, 16 days earlier, had let superheated gas into the wing during re-entry.

The independent board that investigated the Columbia disaster recommended short-term goals that included preventing foam damage and inspecting and repairing shuttles in orbit. For the long term, the board recommended measures to fix the ''broken safety culture'' that it said had led to the disaster. The 15 return-to-flight recommendations, the report said, represented ''the minimum that must be done to essentially fix the problems that were identified by this accident.''

The agency's administrator, Sean O'Keefe, repeatedly vowed that NASA would, as he put it in June 2003, ''comply fully without any equivocation'' with the board's recommendations.

But since then, NASA officials have distanced themselves from those promises, arguing that by making significant strides on many safety issues the need to completely fulfill every recommendation was not as pressing.

The head of the accident investigation board supports the agency's view, as does a panel formed by NASA to monitor its progress in meeting the recommendations. But another board member and several NASA employees disagree. Their concerns include the following:

The accident board recommended that NASA develop a ''practicable capability'' for on-orbit inspection and repair. NASA now says that initially it will be able to make only small repairs in space. For one thing, a multimillion-dollar ''goo gun'' has proved disappointing. Allard Beutel, a NASA spokesman, said the word ''practicable'' provided a degree of flexibility in fulfilling the recommendations.

In addition, the board called for sharp reductions in the amount of foam that might fall off of the external tank and strike the tiles and panels protecting the craft, but agency documents suggest that efforts to limit the size of pieces are still fraught with uncertainty, and in internal NASA presentations, engineers contend that they cannot be sure the upgraded inspection capability will allow them to detect all damage, or determine what requires repair.

Then, too, there is the plan for astronauts to use the International Space Station as a ''safe haven'' from a damaged shuttle, a goal not required by the accident investigation board but taken on by NASA as a way to improve safety. The plan would have little chance of success under many circumstances envisioned by the agency itself, according to internal agency documents and Sergei K. Krikalev, the veteran Russian astronaut who will be commander on the next shift on the station and who echoed the view in comments this month to reporters.

NASA appointed a task force to monitor its progress in complying with the recommendations of the accident board. That task force, led by two former astronauts, Richard O. Covey and Thomas Stafford, is expected to make its final determination of NASA's progress next month, but it already appears to be willing to allow NASA some slack. In a report on Jan. 28, it said that the work left undone included ''some of the toughest technological challenges the recommendations present,'' and that the accident board's recommendations need not be carried out to the letter so long as the activities resulted in ''reduced risk'' over all.

But the Stafford-Covey return-to-flight group raised concerns that NASA was basing many of its claims of increased safety, including critical questions about where debris would strike the orbiter, on the use of computer models instead of physical testing. And it added, ''NASA must be vigilant to prevent the development of a false sense of security by accepting faulty assumptions or otherwise inappropriate analyses, to justify return to flight.''

NASA officials say that no shuttle mission can be risk-free and that the agency has generally raised safety levels enough to justify a return to flight. That assertion is supported by Harold W. Gehman, the retired admiral who was chairman of the Columbia Accident Investigation Board.

''I give them a passing grade, over all,'' Admiral Gehman said in an interview, adding that the board's goal was ''breaking the chain'' of problems that led to foam's falling off the fuel tank and striking the craft, so it did not have to do a ''super whiz-bang job of in-orbit repair.''